I would say the worst effect of torture is to the torturer himself. Once you let your hands get a little bloody, then what's the harm in doing it again? Going a little bit further? You're already bad, you've already gone that far, so why make moral objections now? Some kinds of dirt don't wash off, and once someone--someone with power--decides they're already irredeemably dirty, then they have nothing left to lose. I'm sure most of them justify it to themselves--it was necessary, for the greater good, etc, etc--and maybe even they believe it. It's certainly easier for us to think that torturers must be mad, flawed, somehow different from the rest of us because we'd never do that kind of thing. But they're not. Everybody's capable of that, given the right circumstances. The question is, can you stop yourself from doing it once? And if you did it once, can you stop yourself doing it again? Can you live with your actions, or lack of actions? People can recover from being tortured, but I doubt they ever recover from being torturers.